Mariko Doai^{1}, Naoko Tsuchiya^{1}, Hisao Tonami^{1}, and Osamu Tachibana^{2}

^{1}Radiology, Kanazawa Medical University, Kahoku, Japan, ^{2}Neurosurgery, Kanazawa Medical University, Kahoku, Japan

### Synopsis

**The
purpose of this study is to evaluate the utility of histogram analysis of apparent
diffusion coefficient (ADC) value for distinguishing pituitary atypical
adenomas from typical adenomas.
The
ADC maps were reviewed using Ziostation2, and placed a 3D volume-of interest on
the tumor.
The
entire tumor were computed. Histogram parameters were then compared between
atypical adenomas (n=3) and typical adenomas (n=11). Skewness and kurtosis of
ADC histogram were significantly lower for atypical adenoma as compared with
typical adenoma. ADC histogram analysis on the basis of the entire tumor volume
can be useful in distinguishing atypical adenomas from typical adenomas.**### Purpose

Pituitary
atypical adenomas have been referred to have aggressive behavior, such as
invasiveness and high rate of recurrence (1,2). From a clinical point of view,
preoperative discrimination between atypical adenomas and typical adenomas is
important. The purpose of this study is to evaluate the utility of histogram
analysis of apparent diffusion coefficient (ADC) value for distinguishing
pituitary atypical adenomas from typical adenomas (3,4,5).

### Method

Between
2012 and 2015 , eighteen patients with pituitary macroadenoma underwent diffusion-weighted
imaging (TR/TE, 2500/66ms; b values, 0
and 1000 sec/mm

^{2}) and corresponding ADC maps were obtained. Among
them, four cases with extensive cystic or hemorrhagic changes were excluded
from the analysis. In all cases, pathological confirmations including
immunohistochemical examination were obtained from the surgically resected
specimen. The ADC maps were reviewed using Ziostation2 (Ziosoft Inc., Tokyo,
Japan), and placed a 3D volume-of interest (VOI) on the tumor superimposing
contrast enhanced MR images (Figure 1). All ADC values were within in the VOI
were used to compute the average ADC within the tumor. The ADC values were
binned to construct the histogram. Using the histogram mean, mimimum,maximum,
quartile, skewness, kurtosis, and percentile ( 5th,10th,25th,50th,75th, 90th,95th
) of ADC of the entire tumor were computed. Histogram parameters were then compared
between atypical adenomas (n=3) and typical adenomas (n=11).

### Results

Skewness
and kurtosis of ADC histogram were significantly lower for atypical adenoma as
compared
with
typical adenoma ( 0.118 ± 0.493 vs 1.419 ± 0.556×10

^{-6} mm

^{2}/sec, P=0.011; 0.720 ± 0.948 vs 3.479 ± 1.353×10

^{-6} mm

^{2}/sec, P=0.011, respectively). No significant
differences of ADC histogram were found at other parameters (Table
1). Figure 1 show the representative cases.

### Discussion and Conclusion

The
present study showed that histogram parameters including skeweness and kurtosis
had additional value for distinguishing pituitary atypical adenomas from typical
adenomas. Skewness and kurtosis describe the degree asymmetry and sharpness of
a histogram, respectively.
We
hypothesize that the diffusion pattern of the water molecules is more
heterogenous and more non-Gaussian in atypical adenomas than in typical
adenomas.

In
conclusion, ADC histogram analysis on the basis of entire tumor volume can be
useful in distinguishing atypical adenomas from typical adenomas.

### Acknowledgements

No acknowledgement found.### References

1.Zada G, Woodmansee WW, Ramkissoon S, et al. Atypical pituitary adenomas:incidence, clinical characteristics,and implications. J Neurosurg. 2011;114:336-344

2. Matsuno A, Murakami M, Hoya K, et al. Molecular status of pituitary carcinoma and atypical adenoma that contributes the effectiveness of temozolomide. Med Mol Morphol. 2014;47:1-7

3.Mahmoud OM, Tominaga A, Amatya VJ, et al. Role of PROPELLER diffusion-weighted imaging and apparent diffusion coefficient in the evaluation of pituitary adenomas. Eur J Radiol. 2011;80:412-417

4.
Mohamed FF, Abouhashen S. Diagnostic value of apparent diffusion coefficient
(ADC) in assessment of pituitary macroadenoma cosistency.
The
Egyptian Journal of Radiology and Nuclear Medicine.2013;44:617-624

5.Pierallini
A, Caramia F, Falcone C, et al. Pituitary macroadenomas:Preoperative evaluation
of consistency with diffusion-weighted MR imaging-initial experience. Radiology.
2006;239:223-231